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Tropical Depression Eta Forecast Discussion Number 25

2020-11-06 21:59:38| National Hurricane Center (Atlantic)

Issued at 300 PM CST Fri Nov 06 2020 000 WTNT44 KNHC 062059 TCDAT4 Tropical Depression Eta Discussion Number 25 NWS National Hurricane Center Miami FL AL292020 300 PM CST Fri Nov 06 2020 Reports from an Air Force Reserve Hurricane Hunter aircraft indicate that the center of Eta is elongated east-to-west with multiple vorticity centers present. The central pressure is near 1002 mb, and the maximum flight-level winds were 30-35 kt at 1500 ft. There were a few spot reports of 35-45 kt winds from the Stepped Frequency Microwave Radiometer, but these were in areas of heavy rain and their reliability is suspect. Based on these data, the initial intensity is kept at 30 kt. The aircraft data shows that the center is farther south than previously thought, and the initial motion is an uncertain 040/6 kt. There is no change to the previous track forecast philosophy. A developing mid- to upper-level trough over the Gulf of Mexico is expected to steer Eta northeastward for the next 48 h or so with an increase in forward speed. Between 48-72 h, the trough is forecast to become a closed low near south Florida and western Cuba, causing Eta to turn northwestward around and into the low. After 72 h, the merged system is likely to move slowly westward to northwestward. While the guidance is in good agreement on the synoptic evolution, there remain differences in the track forecast details in terms of both the heading and the forward speed, with the GFS-based guidance tending to be to the east and north of the UKMET/ECMWF/Canadian. In addition, the HWRF/HMON/Canadian are faster than the other guidance. The new forecast track overall is a little slower than the previous track, and due to the initial position the first 36 h have been shifted southward. Eta will move over the warm waters of the northwestern Caribbean during the next 48 h or so, and the upper-level divergence is forecast to be quite strong. This should allow some strengthening, although this is likely to be slowed by 20-30 kt of southwesterly vertical wind shear. The intensity forecast for this part of the cyclone's life is again similar to the previous forecast and lies near the bulk of the intensity guidance. Between 48-72 h , Eta may take on at least some subtropical cyclone characteristics as it merges with the mid- to upper-level low. The HWRF and HMON models still suggest the possibility that a tight inner wind core may develop, however, the guidance has trended weaker since this morning, and the new intensity forecast is above the bulk of the guidance. After 72 h, dry air entrainment is expected to cause the cyclone to weaken. The wind field of Eta is expected to increase in size during the next few days, and the cyclone will likely produce a large area of tropical-storm-force winds on its north side when it is near Cuba, the Florida Keys, and southern Florida. The new forecast track requires a Tropical Storm Warning for portions of Cuba at this time. Watches may be required for portions of south Florida and the Florida Keys tonight. Key Messages: 1. Heavy rainfall is diminishing across portions of Central America, although the threat of life-threatening flooding may continue, along with landslides in areas of higher terrain. Heavy rainfall from Eta will move into the Cayman islands and portions of Cuba, resulting in significant, life-threatening flash flooding and river flooding. Flash flooding and urban flooding is also possible for Jamaica and southeast Mexico. 2. Tropical storm conditions are expected this weekend in portions of the Cayman Islands and Cuba, where a Tropical Storm Warning is in effect. 3. There is an increasing risk of impacts from wind and flash and urban flooding due to heavy rainfall in portions of southern Florida, the Florida Keys, and portions of the Bahamas this weekend and early next week. Tropical Storm or Hurricane Watches will likely be issued for a portion of this area tonight. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 17.3N 86.5W 30 KT 35 MPH 12H 07/0600Z 18.2N 84.8W 35 KT 40 MPH 24H 07/1800Z 19.4N 82.5W 40 KT 45 MPH 36H 08/0600Z 20.8N 80.7W 45 KT 50 MPH 48H 08/1800Z 22.5N 80.0W 50 KT 60 MPH...INLAND 60H 09/0600Z 24.2N 80.6W 55 KT 65 MPH...OVER WATER 72H 09/1800Z 24.9N 81.8W 55 KT 65 MPH 96H 10/1800Z 25.0N 84.0W 50 KT 60 MPH 120H 11/1800Z 26.5N 85.5W 50 KT 60 MPH $$ Forecaster Beven

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Tropical Depression Eta Forecast Discussion Number 24

2020-11-06 16:00:33| National Hurricane Center (Atlantic)

Issued at 900 AM CST Fri Nov 06 2020 417 WTNT44 KNHC 061500 TCDAT4 Tropical Depression Eta Discussion Number 24 NWS National Hurricane Center Miami FL AL292020 900 AM CST Fri Nov 06 2020 Satellite imagery indicates that Eta is producing organized convection in a large band over its northern and eastern quadrants, with the center located just off the coast of Belize near the western end of the band. These data, along with surface observations, also show that the circulation is elongated. The initial intensity remains 30 kt in agreement with a satellite intensity estimate from TAFB. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Eta this afternoon, and a NOAA flight is scheduled for this evening. The initial motion is a somewhat uncertain 025/6 kt. A developing mid- to upper-level trough over the Gulf of Mexico is expected to steer Eta northeastward for the next 48 h or so with an increase in forward speed. Between 48-72 h, the trough is forecast to become a closed low near south Florida and western Cuba, with Eta expected to turn northwestward around and into the low. After 72 h, the merged system is likely to move slowly west-northwestward. While the guidance is in good agreement on the synoptic evolution, there are a lot of differences in the track forecast details in terms of both the heading and the forward speed, with the GFS-based guidance tending to be to the east and north of the UKMET/ECMWF/Canadian. Overall, the consensus models have shifted a little to the east and north since the last advisory, and the new forecast track is also nudged in those directions. Eta will move over the warm waters of the northwestern Caribbean during the next 48 h or so, and the upper-level divergence is forecast to be quite strong. This should allow some strengthening, although this is likely to be slowed by 20-30 kt of southwesterly vertical wind shear. The intensity forecast for this part of the cyclone's life is similar to the previous forecast and lies a bit below the bulk of the intensity guidance. Between 48-72 h , Eta may take on at least some subtropical cyclone characteristics as it merges with the mid- to upper-level low. During this process, some of the guidance suggests the possibility that a tight inner wind core may develop. There is a chance that during this time that Eta could regain hurricane strength, although this would be an intensity above the current guidance. After 72 h, dry air entrainment is expected to cause the cyclone to weaken. The wind field of Eta is expected to increase in size during the next few days, and the cyclone will likely produce a large area of tropical-storm-force winds on its north side when it is near Cuba, the Florida Keys, and southern Florida. The new forecast track requires a Tropical Storm Warning for the Cayman Islands at this time, and a Tropical Storm Watch for portions of Cuba. Watches may be required for portions of south Florida and the Florida Keys later today or tonight. Key Messages: 1. Rainfall associated with Eta will continue to result in catastrophic, life-threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Significant, life-threatening flash flooding and river flooding is possible in the Cayman Islands and Cuba. Flash flooding and urban flooding is also possible for Jamaica and southeast Mexico. 2. This weekend Eta is expected to bring tropical storm conditions to portions of the Cayman Islands, where a Tropical Storm Warning is in effect. Tropical storm conditions possible in portions of western and central Cuba, where a Tropical Storm Watch is in effect. 3. There is an increasing risk of impacts from wind and flash and urban flooding due to heavy rainfall in portions of southern Florida, the Florida Keys and portions of the Bahamas this weekend and early next week. Tropical Storm or Hurricane Watches will likely be issued later today or tonight for a portion of this area. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 17.8N 87.0W 30 KT 35 MPH 12H 07/0000Z 18.6N 85.7W 35 KT 40 MPH 24H 07/1200Z 19.7N 83.5W 40 KT 45 MPH 36H 08/0000Z 21.0N 81.4W 45 KT 50 MPH 48H 08/1200Z 22.7N 79.9W 50 KT 60 MPH...INLAND 60H 09/0000Z 24.1N 80.0W 55 KT 65 MPH...OVER WATER 72H 09/1200Z 25.0N 81.2W 55 KT 65 MPH 96H 10/1200Z 25.5N 84.0W 50 KT 60 MPH 120H 11/1200Z 26.5N 85.0W 50 KT 60 MPH $$ Forecaster Beven

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Tropical Depression Eta Forecast Discussion Number 23

2020-11-06 09:36:58| National Hurricane Center (Atlantic)

Issued at 300 AM CST Fri Nov 06 2020 000 WTNT44 KNHC 060836 TCDAT4 Tropical Depression Eta Discussion Number 23 NWS National Hurricane Center Miami FL AL292020 300 AM CST Fri Nov 06 2020 Although satellite images and surface observations suggest that the circulation of Eta is elongated, deep convection has been increasing near and over the center during the past several hours. Unfortunately, the ASCAT scatterometer missed the region where Eta is located, so there has not been much additional data to analyze the structure and intensity of the cyclone. The initial wind speed is held at 30 kt based on a 2.0/30 kt Dvorak classification from TAFB. The NOAA and Air Force Hurricane Hunters are scheduled to investigate Eta later today, and that data will be helpful in analyzing the cyclone. The depression is moving northward at 7 kt. Eta is forecast to turn northeastward later today, and accelerate slightly in that direction through Saturday in response to a mid- to upper-level trough that is expected to slide southeastward across the Gulf of Mexico. This motion should take Eta to the west of the Cayman Islands on Saturday and then across Cuba Saturday night or Sunday. Around the time Eta is forecast to be near Cuba, the models show the storm slowing down and turning northwestward or westward as the trough cuts off, and Eta pivots around the north side of that cut off low. This change in the storm motion should bring Eta near or over the Florida Keys and south Florida late in the weekend and early next week. The details in the location and timing of where Eta and the mid- to upper-level low interact will be very important to the exact track of Eta for south Florida and the Florida Keys. The new track forecast is a touch to the north of the previous one when Eta is expected to be near Florida, to be in better agreement with the latest consensus aids. The cyclone is currently over warm water, in a moist environment, and will be moving into a region of upper-level diffluence as it tracks across the northwestern Caribbean Sea. These conditions should allow for thunderstorms to organize near the center and for the cyclone to gradually intensify during the next couple of days. However, rapid intensification seems unlikely given the broad structure of Eta. The models show an increase in shear and some dry air entraining into the circulation around the time it nears Cuba this weekend, which in combination with land interaction could limit additional strengthening by then. The intensity forecast for the 72-120 hour period is more complicated as it will depend on the trough interaction mentioned above. Most of the intensity models show Eta holding steady in strength after its passage over Cuba, and the NHC forecast does the same. The wind field of Eta is expected to increase in size during the next few days, and the cyclone will likely produce a large area of tropical-storm-force winds on its north side when it is near Cuba, the Florida Keys, and southern Florida. Key Messages: 1. Through Monday morning, heavy rainfall from Eta will lead to catastrophic, life-threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Flash and river flooding is also possible across Jamaica, southeast Mexico, the Cayman Islands and western Cuba. 2. Eta is forecast to regain tropical storm strength over the northwestern Caribbean Sea later today. Although the details of the future track and intensity of Eta are still uncertain, there is an increasing risk of impacts from wind and rainfall in portions of the Cayman Islands, Cuba, southern Florida and the Florida Keys and the northwestern Bahamas this weekend and early next week. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 17.3N 87.4W 30 KT 35 MPH 12H 06/1800Z 18.0N 86.6W 35 KT 40 MPH 24H 07/0600Z 19.1N 84.5W 40 KT 45 MPH 36H 07/1800Z 20.2N 82.2W 45 KT 50 MPH 48H 08/0600Z 21.8N 80.3W 50 KT 60 MPH 60H 08/1800Z 23.5N 79.9W 55 KT 65 MPH 72H 09/0600Z 24.6N 80.7W 55 KT 65 MPH 96H 10/0600Z 25.1N 83.7W 55 KT 65 MPH 120H 11/0600Z 25.9N 85.0W 55 KT 65 MPH $$ Forecaster Cangialosi

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Tropical Depression Eta Forecast Discussion Number 22

2020-11-06 03:54:23| National Hurricane Center (Atlantic)

Issued at 900 PM CST Thu Nov 05 2020 000 WTNT44 KNHC 060254 TCDAT4 Tropical Depression Eta Discussion Number 22 NWS National Hurricane Center Miami FL AL292020 900 PM CST Thu Nov 05 2020 Eta has not become any better organized during the past several hours, and a specific center is hard to locate. It is estimated that the center is near a growing area of deep convection located east of the Belize. While it is possible the system has degenerated into a broad low or trough, there isn't enough evidence to break continuity, so Eta remains a 30-kt tropical depression on this advisory. Scatterometer data will probably come in overnight to provide a better look at the low-level circulation. The initial motion is an uncertain 360/7 kt. Eta should move northeastward on Friday around a developing mid- to upper-level trough over the Gulf of Mexico, then turn northward on Sunday and west-northwestward early next week as the trough cuts off into a closed low. The details of this sinuous path, however, are pretty fuzzy and small differences in the tropical cyclone position could lead to large errors down the line. The most notable change tonight is that the GFS-based guidance (including HWRF and HMON) have generally shifted northward and faster. The new forecast is moved eastward near Cuba, and then northward near the Florida Keys in response to this guidance and the 18Z ECMWF. It should be stressed this is a fairly uncertain forecast due to the strong trough interaction. Eta should begin to strengthen on Friday due to the low-level circulation forecast to become better defined in a fairly conducive environment. While vertical wind shear could increase this weekend, it is expected that upper-level divergence and trough dynamics will overwhelm the negative factors and cause continued intensification until the system reaches Cuba. The new forecast is raised from the previous one, but still lies below the NOAA corrected-consensus model HCCA. There isn't a lot of agreement on the intensity after Cuba, however, and the forecast hinges on how tropical it will remain after the trough interaction. The new forecast flattens out the intensity near Florida as a compromise between the various solutions, but I don't have much confidence in the forecast at that range. Key Messages: 1. Through Monday morning, heavy rainfall from Eta will lead to catastrophic, life-threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Flash and river flooding is also possible across Jamaica, southeast Mexico, the Cayman Islands and western Cuba. 2. Eta is forecast to regain tropical storm strength over the northwestern Caribbean Sea on Friday. Although the details of the future track and intensity of Eta are uncertain, there is an increasing risk of impacts from wind and rainfall in portions of the Cayman Islands, Cuba, southern Florida and the Florida Keys and the northwestern Bahamas this weekend and early next week. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 16.6N 87.8W 30 KT 35 MPH 12H 06/1200Z 17.5N 87.2W 35 KT 40 MPH 24H 07/0000Z 18.8N 85.4W 40 KT 45 MPH 36H 07/1200Z 19.7N 83.2W 45 KT 50 MPH 48H 08/0000Z 20.8N 81.0W 55 KT 65 MPH 60H 08/1200Z 22.6N 79.8W 50 KT 60 MPH...INLAND 72H 09/0000Z 24.2N 80.4W 55 KT 65 MPH...OVER WATER 96H 10/0000Z 25.0N 83.0W 55 KT 65 MPH 120H 11/0000Z 25.5N 85.0W 55 KT 65 MPH $$ Forecaster Blake

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Post-Tropical Cyclone Odalys Forecast Discussion Number 10

2020-11-06 03:32:26| National Hurricane Center (East Pacific)

Issued at 700 PM PST Thu Nov 05 2020 000 WTPZ45 KNHC 060232 TCDEP5 Post-Tropical Cyclone Odalys Discussion Number 10 NWS National Hurricane Center Miami FL EP202020 700 PM PST Thu Nov 05 2020 Odalys has been devoid of any significant convection within 100 n mi of the center for more than 12 hours, and the system no longer meets the satellite-based criteria of a tropical cyclone. The initial intensity of 30 kt is based on an expected gradual spin down of the circulation, which is supported by a Dvorak current-intensity satellite classification of T2.0/30 kt. An earlier 1725Z ASCAT-A pass contained a small patch of 34-kt winds located northwest of the center, and there is currently no convection in that same sector of the cyclone. Post-tropical Odalys is currently located over marginal 26-deg-C sea-surface temperatures and within a very hostile vertical wind shear regime. The shear is expected to increase from the current 35 kt to more than 40 kt by 24 hours, which should prevent any significant and/or persistent convection from redeveloping near the low-level center. As a result, Odalys should continue to weaken and dissipate by 72 hours, if not sooner. The initial motion estimate is 270/07 kt. A westward motion should continue tonight, followed by a turn toward the west-southwest or southwest by Friday afternoon, with that motion continuing into the weekend until Odalys dissipates. The NHC official forecast track is similar to the previous advisory track, and lies close to the consensus track model TVCE. This is the last advisory issued by the National Hurricane Center on Odalys. For additional information on the remnant low, please see High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 18.6N 124.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 12H 06/1200Z 18.3N 125.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 07/0000Z 17.6N 125.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 07/1200Z 17.0N 126.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 08/0000Z 16.4N 127.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 08/1200Z 15.9N 127.9W 15 KT 15 MPH...POST-TROP/REMNT LOW 72H 09/0000Z...DISSIPATED $$ Forecaster Stewart

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